Pump



y ,1969 J. M. SPURLOCK ETAL 3,453,967

PUMP

Filed Sept. 15, 1967 INVENTORS L/ACX M SPURLOCK ATTORNEYS United States Patent 3,453,967 PUMP Jack M. Spurlock, Springfield, and Robert L. Durfee, An-

nandale, Va., assignors, by mesne assignments, to

Electro Medical Systems, Inc., a corporation of Colorado Filed Sept. 15, 1967, Ser. No. 667,947 Int. Cl. F041) 43/00 US. Cl. 103-448 9 Claims ABSTRACT OF THE DISCLOSURE This invention is a positive displacement pump which exerts minimum traumatic effects on liquids being handled. The pump is characterized by a deformable conical chamber having inlets and outlets fitted with one-way valves. Pumping action is provided by means for reciprocally twisting the chamber.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to positive displacement pumps. More particularly, it relates to pumps suited for applications where it is desired that the fluid being pumped is subjected to minimum trauma.

Applications for such pumps are emexplified in the handling of shock and friction sensitive materials such as nitroglycerine, various pumpable liquid, gel, or slurry explosives or propellants, and in procedures requiring circulation of trauma-sensitive body fluids such as blood. In the latter application excessive trauma exerted on blood by shear, impact, turbulence, etc. during pumping damages the protective skin of the red blood cells causing release of hemoglobin to the plasma-a deleterious process known as hemolysis.

Since, in the pumping of blood, the traumatic effect of the pump can be determined by routine hemolysis tests and compared with hemolysis data published for previously known pumps, theinvention is hereinafter described by reference to embodiments particularly adapted to blood pumping. It will be recognized, however, that the pump of this invention has utility in numerous other applications having some or all of the requirements present in extracorporeal circulation processes.

Description of the prior art Pumps previously used for extracorporeal circulation of blood include finger pumps wherein the successive occlusion of the tube by a series of cam operated fingers produces a positive displacement to efifect unidirectional flow through the tube; roller pumps wherein a rotating armature containing one or more rollers compresses the walls of circular tubing to propel fluids therethrough; pumps wherein bladders fitted with inlet and outlet valves are alternately compressed and released; and pumps wherein the fluid is moved by the action of a flexible diaphram. Such pumps have proven generally satisfactory for augmenting or replacing the action of an animal heart during operations of short duration. However, procedures requiring prolonged periods of extracorporeal circulation are often complicated by the high hemolysis levels produced by continuous pumping.

SUMMARY OF THE INVENTION It is an object of this invention to provide pumps which exert minimal traumatic action on the liquid being handled. Further, it is an object of the invention to provide pumps having pulsatile characteristics that can be conveniently modified for adaption to specific applicaa 3,453,967 Patented July 8, 1969 tions. These and other objects are accomplished by the pump of this invention at least in part through minimization of shearing action, impact. forces, and undesirable turbulent flow patterns.

Basically, the pump comprises a deformable conical chamber, preferably substantially vertically-oriented. The chamber is provided with inlet and outlet passages fitted with one-way valves. Preferably these passages are oriented in the direction of internal flow patterns produced by the pump in order to minimize directional changes in fluid flow and resulting turbulence. Pumping action is provided by deforming the conical chamber from the apex toward the base so as to induce spiraling flow of fluid.

The structure and operation of the pump and additional advantages thereof will be understood from the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an exploded representation of the preferred embodiment of this invention. FIGURE 2 is an illustration of the pump of this invention during an operating cycle. FIGURE 3 is a top plan view of the inside of the pumping chamber during an operating cycle.

DESCRIPTION OF THE PREFERRED EMBODIMENT This pump is of the positive displacement type. The principal object in this novel design is to provide smooth, uninterrupted flow patterns which minimize fiuid-to-fluid and fluid-to-sidewall contact, and abrupt changes in direction of the flow stream. As shown in FIGURE 1, the primary element in the pump is a cone-shaped pumping chamber 10 made from a deformable material such as a natural or synthetic polymer. The interior wall of chamber 10' is smooth in keeping with the promotion of laminar flow with minimum sidewall friction. Both the inlet passage 12 and the outlet passage 13 are tangentially oriented with respect to the interior sidewall of the pumping chamber to inject and remove the fluid being pumped without abrupt changes in flow direction. In keeping with the principles of operation of a positive displacement pump, the pumping chamber must be isolated by one-way valves such as flat valves 14. Pumping action is caused by deforming pumping chamber 10 inward and upward from the apex. A. preferred means for doing this is by a twisting motion caused by an apparatus attached to a cylindrical extension 16 protruding from the apex of chamber 10. Chamber 10 is also provided with a closure 18 which can be a separate component or which can be molded as an integral part of the chamber. Inlet passage 12 can be an integral part of cone 10, or it can be, as shown, part of the closure 18. In either case, inlet passage 12 communicates with the pump chamber at an acute angle so that it injects the fluid being pumped tangentially into the chamber. In addition, inlet passage 12 is oriented in the opposite direction from outlet passage 13, so that a spiraling flow stream is established in the pump chamber.

The twisting motion which causes the pumping action in the example shown in FIGURE 1 can be provided by any means such as a motor with a cammed fly wheel and connecting rod, not shown, attached to pumping chamber 10 by means of a lever 24 and actuator 26 which grasps extension 16 of the chamber. The pumping chamber is twisted a predetermined degree in the same direction as the spiral flow of the fluid being pumped and with each stroke displaces a fixed amount of fluid.

As pump chamber 10 is twisted, it deforms inwardly, {forming a number of lobes which extend upwardly toward the base portion of the cone as the amount of twist is increased. In order to precisely control this inward lobular deformation and to prevent outward distension, an external, rigid, truncated cone 28 is fixedly attached to acturator 26. The height of this element 28 in relation to the size and configuration of pump chamber 10, controls the number of lobes created.

FIGURES 2 and 3 show the lobe pattern at maximum twist in an embodiment designed so that the deformation of chamber 10 creates three lobes. These lobes 30 deform inwardly, thus decreasing the volume of pump chamber 10 and forcing a measured amount of fluid out with each twisting stroke. The direction in which chamber 10 is twisted determines the direction in which the liquid being pumped will move; it is complementary with the orentation of the inlet passage and outlet passage and a smooth spiral flow is created. By controlling the interrelationship between the configuration of pump chamber 10, the height of truncated cone 28, and the degree of twist imparted to the pump chamber, lobes 30 can be precisely created. This precise control of the formation of the lobes insures that there is minimum chance of touching of the sidewalls, which would disrupt the laminar flow and injure the fluid being pumped.

As can be seen by an analysis of this novel design, the fluid undergoes no abrupt change of direction from inlet to outlet of the pump. The flow path is a tangential injection along the sidewalls of a smooth cone, around the sidewalls of the cone in a spiral, and a tangential exit from the cone. Pumping action is provided by pushing the fluid being pumped upward and around in a spiraling motion, in response to the controlled deformation inward of the lower portion of the pump chamber.

In addition to the basic elements of the pump, above described, certain modifications can be made insofar as the manner in which the twisting movement is applied to pump chamber 10, the manner in which the inlet and outlet ports are in communication with the pump chamber consistent with providing smooth laminar flow without abrupt change of direction, and the manner in which the predetermined numbers of lobular deformations having precise configurations are produced. For example, rather than the mechanical twisting operation provided by elements 24 and 26 in combination with a motor, the deformation pattern could be created by providing a snakelike expanding helix tube around the pump chamber, with pulses of hydraulic fluid being provided to the helix in such a manner as to deform the lower portion of cone 10 inward. It is also possible to accomplish this deformation by means of a helical spring, which is twisted from the apex of the cone in such a manner as to provide the desired inward deformation. In addition, the concept is not limted to the three lobes shown in FIGURE 2, but works equally well with other numbers. By control of rate, degree, and force of chamber deformation, desired pulsatile flow characteristics are readily obtained.

It is also possible to provide this novel pump with a number of accessories in order to take advantage of its pumping characteristics. For example, under most circumstances it is desirable to control the stroke so that only the liquid in the upper portion of pump chamber 10 is moved through the pump. This means that the fluid in the lower portion is somewhat stagnant and, therefore, by controlling the velocity of the flow through the pump, solid particles or heavy liquids can be precipitated out of the flow stream, means being provided at the bottom of cone 10 to then remove them from the pump chamber, either continuously or intermittently.

The advantages and characteristics of the pump of this invention will be further understood from the following example.

Example I Standard reagent dog blood treated with acid-citratedextrose anti-clotting solution and containing approximately 36% by volume red blood cells was pumped at a rate of about 3.25 liters per minute for about two hours with a pump as shown in FIGURE 1. The pump utilized a silicone rubber conical chamber with a capacity of about 175 ml. The pump was actuated by a reciprocal twisting action of about which, in combination with the truncated external cone 28, resulted in tri-lobular deformation sufiicient to displace about 49 ml. of fluid per cycle.

The hemolysis index-that is, the grams of hemoglobin released per liters of fluid pumpedwas determined by the method of Flink and Watson (A Method for the Quantitative Determination of Hemoglobin and Related Heme Pigments in Feces, Urine, and Blood Plasma, J. Biol. Chem. 146, pp. 171-178 (1942)), to be 0.023 gm./ 100 liters.

For purposes of comparison, hemolysis indices of several commercially available heart pumps as determined by the same method and reported in the literature (Mechanical Devices to Assist the Failing Heart, Publication 1283, National Academy of Sciences-National Research glciuncil, Washington, DC, 1966) are shown in Table I e ow:

Thus, it is seen that the pump of this invention produces from about 2 to 10 times less hemolysis than hitherto known commercially available pumps.

Although this invention has been described in terms of preferred embodiments, various modifications thereto within the scope of the appended claims will be apparent to those skilled in the art.

What is claimed is:

1. A positive displacement pump comprising a deformable cone-shaped pumping chamber having a closed base,

a valved, one-way inlet passage disposed adjacent said base and communicating with said chamber, a valved, one-way outlet passage disposed adjacent said base and communicating with said chamber, and

means for progressively twisting said chamber inwardly from the apex toward the base to create a spiral fluid flow in said chamber from said inlet passage to said outlet passage.

2. The pump of claim 1 wherein said twisting means is cyclical in operation.

3. The pump of claim 2 wherein said means for cyclically twisting said chamber is adapted to engage the apex of said chamber.

4. The pump of claim 2 further comprising means surrounding at least a portion of said chamber and confining said chamber against outward distension during twisting thereof. 5. The pump of claim 4 wherein said chamber-confining means comprises a section of a truncated cone secured to said twisting means and extending from the apex a predetermined distance along said chamber wall in juxtaposition therewith.

6. The pump of claim 1 wherein said inlet passage and said outlet passage are oriented substantially in the direction of the flow stream created in said chamber to minimize changes in the direction of fluid flow.

7. The pump of claim 6 wherein said inlet passage and said outlet passage communicate with the portion of said chamber not deformed by said twisting means during the pumping action.

8. The pump of claim 1 wherein said outlet passage is oriented substantially tangential to the side of said chamger and substantially parallel to the base of said cham- References Cited UNITED STATES PATENTS 1,117,779 11/1914 Bulmer 103-14s 1,491,860 4/1924 Holden 222-404 2,080,134 2/1937 Jena--1; 222-104 Rymal 103-148 Bower 103--148 Trout et a1. 103148 Landenberger 230-160 Pasquali et al. 103-448 DONLEY J. STOCKING, Primary Examiner.

W. J. GOODLIN, Assistant Examiner. 

